This invention relates to an improved ceramic filter for use in ultrafiltration or precision-filtration.
A conventional filter for ultrafiltration or precision-filtration has a separation layer such as a synthetic organic film such as cellulose acetate, PVA and nylon; or a filter cloth coated with a filtration auxiliary such as diatomaceous earth. Such a separation layer is used as a full forced-flow filter.
The synthetic film has a poor strength so that the pressure difference must be 20 kgf or less. It cannot be used for a long time at a temperature of 50.degree. C. or more. It cannot be used for the purpose of filtering an acid solution. Back washing is not effective in case of the conventional forced filtering.
Recently, ceramic filters have been proposed because they have a good strength, heat resistance or chemical resistance and can be easily formed in a pipe shape. Also, as cross-flow filtration is possible, back washing is effective. However the conventional ceramic filters do not have all of the desired strength, filtration rate and accuracy characteristics.